In order to observe fine areas in objects, there have been used scanning electron microscopes (SEMs), transmission electron microscopes (TEMs) and the like. In general, these devices are adapted to evacuate a casing for placing a sample therein for bringing the ambience around the sample into a vacuum state and, further, are adapted to capture images of the sample. However, biochemical samples, liquid samples and the like are damaged or changed in state by the vacuum. On the other hand, there have been greater needs for observing such samples with electron microscopes and, in recent years, there have been developed SEM devices, sample holding devices and the like which enable observations of to-be-observed samples under an atmospheric pressure.
These devices are adapted, in principle, to separate a vacuum state and an atmospheric-air state from each other, through a diaphragm capable of transmitting electron beams therethrough, which is provided between an electrooptic system and a sample. These devices have a commonality in that they all have the diaphragm provided between the sample and the electrooptic system.
For example, PTL 1 discloses a SEM including an electrooptic barrel placed such that an electron source therein is faced downwardly and, also, an objective lens therein is faced upwardly, and a diaphragm capable of transmitting electron beams therethrough, which is provided on an electron-beam emitting hole at the distal end of the electrooptic barrel with an O ring interposed therebetween. The invention described in this literature is adapted to place a liquid containing a to-be-observed sample, directly, on the diaphragm further to direct a primary electron beam to the sample at its lower surface and to detect reflected electrons or secondary electrons for attaining SEM observations. The sample is held in the space formed by the diaphragm and an annular member installed around the diaphragm and, further, this space is interiorly filled with a liquid such as water.